Electrical conductivity and electromagnetic interference shielding of polyaniline/polyacrylate composite coatings

Lightweight and flexible composite coatings of p-toluene sulfonic acid doped polyaniline (PANT-TSA) with various mass fractions and polyacrylate were prepared for electromagnetic interference (EMI) shielding. Both the volume and surface conductivities of the composite coatings increased with increasing PANI-TSA; furthermore, the volume conductivity showed a typical percolation behavior with a percolation threshold at about 0.21. The EMI shielding effectiveness (SE) of the PANI-TSA/polyacrylate coatings over the range of 14 kHz to 15 GHz increased with increasing PANI-TSA as the direct-current conductivity did. EMI SE of the coatings at the low frequencies (14 kHz to I GHz) was around 30-80 dB, higher than that at the high frequencies (1-15 GHz); this indicated possible commercial application of the coatings for far-field EMI shielding. The highest EMI SE value was 79 dB at 200 MHz with a coating thickness of 70 +/- 5 mu m. The moderate SE, light weight, and easy preparation of the coating are advantages for future applications for EMI shielding. (c) 2005 Wiley Periodicals, Inc.